1. Field of the Invention
The present inventions relate to a clutch engagement control system, and more specifically, to a clutch engagement control system that can reduce the time required for engaging the friction clutch by increasing velocity to engage the friction clutch until the friction clutch starts transmitting power.
2. Background Art
FIG. 4 is a schematic sectional view illustrating a conventional clutch engagement control system 200.
The conventional clutch engagement control system 200 controls engagement of a friction clutch 1 used for motorcycles by means of an actuator 3 The friction clutch 1 is engaged or disengaged to transmit or not to transmit torque from an engine crankshaft (not shown) to a mission shaft 7 made up of a drive shaft of a multistage transmission 5, a type of transmission. Torque transmitted to the mission shaft 7 is transmitted to a countershaft 9 interlocked with the mission shaft 7 via the multistage transmission 5.
The torque transmitted to the countershaft 9 is further transmitted to a rear wheel 13, which is a drive wheel of the motorcycle, via a countershaft sprocket 11. The countershaft sprocket 11 is integrally provided with the countershaft 9 on one end of the countershaft 9. A rear wheel sprocket 17 supporting the rear wheel 13 and integrally provided with a rear wheel shaft 15 transmits drive torque to the rear wheel 13. A chain 19 wrapped around the countershaft sprocket 11 and the rear wheel sprocket 17 transmits torque from the countershaft sprocket 11 to the rear wheel sprocket 17.
The mission shaft 7 and the countershaft 9 are rotatably disposed in an engine gearcase CS1 for the motorcycle while the shaft of the rear wheel 13 is rotatably disposed for free rotation on a frame body (see FIG. 3) for the motorcycle.
The friction clutch 1 is configured to gradually transmit the drive force (torque) produced by the engine to the multistage transmission 5 to allow the motorcycle to smoothly start, and to temporarily disengage the power transmitted between the engine and the multistage transmission 5 to allow gear changes.
The friction clutch 1 may be a multiplate friction clutch For example, friction clutch 1 can comprise an outer driver 23 integrally provided with a gear 21 that engages with a gear (not shown) integrally supported by the engine crankshaft and that is disposed for free rotation around the mission shaft 7. As such, the mission shaft 7 receives torque transmitted from the crankshaft A plurality of friction discs 25 or friction plates are integrally mounted to the outer driver 23. A plurality of clutch plates 29 or friction plates are integrally mounted to an inner driver 27. The inner driver 27 receives torque transmitted from the outer driver 23 by frictional force generated between the plurality of friction discs 25 and the plurality of clutch plates 29.
The gear 21 is provided for free rotation on one end of the mission shaft 7. The outer driver 23, mounted integrally to a boss portion of the gear 21, is restricted to displace the mission shaft 7 in the rotational axis direction while being rotatable around the mission shaft 7. The inner driver 27 is mounted integrally to one end of the mission shaft 7 (furthest end from the gear 21).
The friction clutch 1 may be a multiplate friction clutch. For example, friction clutch 1 can comprise an outer driver 23 integrally provided with a gear 21 that engages with a gear (not shown) integrally supported by the engine crankshaft and that is disposed for free rotation around the mission shaft 7. As such, the mission shaft 7 receives torque transmitted from the crankshaft. A plurality of friction discs 25 or friction plates are integrally mounted to the outer driver 23. A plurality of clutch plates 29 or friction plates are integrally mounted to an inner driver 27. The inner driver 27 receives torque transmitted from the outer driver 23 by frictional force generated between the plurality of friction discs 25 and the plurality of clutch plates 29.
The cylindrical outer driver 23 has an opening on its one end, which is provided with an engaging portion 23B having an engaging hole 23A that engages with a circular engaging projection 21A disposed in the boss portion of the gear 21. The engaging portion 23B having the engaging hole 23A allows the outer driver 23 to be fixed concentrically to the gear 21.
The friction discs 25 are ring-shaped thin plates and an outer peripheral edge of each friction disc 25 is supported by an inner periphery of the cylindrical outer driver 23 such that the plane of each friction disc 25 is generally perpendicular to the rotational axis direction of the mission shaft 7. Such support allows each friction disc 25 to be slightly movable in the rotational axis direction of the mission shaft 7 relative to the outer driver 23 while its rotation in the rotational direction of the mission shaft 7 relative to the outer driver 23 is restricted
A predetermined space (with a little longer length than the thickness of the clutch plate 29) is defined between the adjacent planes of the friction discs 25.
The cylindrical inner driver 27 has an opening on one end provided with a circular flange 27A having approximately same outside diameter as the clutch plate 29, and also supports the plurality of clutch plates 29 with its cylindrical outer periphery. Such support allows each clutch plate 29 to be slightly movable in the rotational axis direction of the mission shaft 7 relative to the inner driver 27 while restricts its rotation in the rotational direction of the mission shaft 7 relative to the inner driver 27.
The inner driver 27 is fixed to one end of the mission shaft 7 with its flange 27A located on the side of the engaging portion 23B of the outer driver 23.
The clutch plates 29 are ring shaped thin plates, and an inner peripheral edge of each clutch plate 29 is supported with an outer periphery of the cylindrical inner driver 27 as described above such that the plane of each clutch plate 29 is generally perpendicular to the rotational axis direction of the mission shaft 7.
A predetermined space (with a little longer length than the thickness of the friction disc 25) is defined between the adjacent planes of the clutch plates 29.
Each of the clutch plates 29 has an outside diameter slightly smaller than the inside diameter of the cylindrical outer driver 23. Each of the friction discs 25 has an inner diameter slightly larger than the outside diameter of the cylindrical inner driver 27.
The friction discs 25 and the clutch plates 29 are alternately located in the rotational axis direction of the mission shaft 7. A small space is defined in the rotational axis direction of the mission shaft 7 between each friction disc 25 and clutch plate 29.
A pressing portion 27B including the flange 27A of the inner driver 27, is provided on outer sides of each friction disc 25 and clutch plate 29 located alternately as described above as well as on outer sides of the rotational axis direction of the mission shaft 7 and on the side of the engaging portion 23B of the outer driver 23. The friction discs 25 and the clutch plates 29 are interposed between the pressing portion 27B and a pressure plate 31, to be discussed later, in the rotational axis direction of the mission shaft 7 to generate frictional force between each friction disc 25 and clutch plate 29. The pressing portion 27B is generally a plane approximately parallel to each plane of the friction discs 25 and the clutch plates 29.
The friction clutch 1 is provided with a circular pressure plate 31 on the outsides of each friction disc 25 and clutch plate 29 located alternately as described above as well as on the outer sides of the rotational direction of the mission shaft 7 and on the opposite side of the engaging portion 23B of the outer driver 23.
The pressure plate 31 is provided with a plurality of guide portions 31A disposed integrally with the cylindrical inner driver 27 inside of the inner driver 27 and engaging with plural cylindrical guide portions 27C which extend in the rotational axis direction of the mission shaft 7. The guide portions 27C and the guide portions 31A allow the pressure plate 31 to be located movably in the rotational axis direction of the mission shaft 7 relative to the inner driver 27 as well as to rotate together with the inner driver 27.
The pressure plate 31 has a plane pressing portion 31B approximately parallel to each plane of the friction discs 25 and the clutch plates 29.
Plural compression springs 33 are provided so as to respectively enclose the plurality of cylindrical guide portions 27C. The pressure plate 31 is urged by each compression spring 33 in the direction in which the pressing portion 31B of the pressure plate 31 approaches the pressing portion 27B of the inner driver 27.
When the friction clutch I is being engaged, the pressure plate 31 is displaced and urged toward the flange 27A of the inner driver 27 by the compression springs 33. The friction discs 25 and the clutch plates 29 are interposed and pressed between the pressing portion 27B of the inner plate 27 and the pressing portion 31B of the pressure plate 31 to generate frictional force between each friction disc 25 and clutch plate 29. This allows torque to be transmitted from the outer driver 23 to the inner driver 27.
On the other hand, when the friction clutch 1 is being disengaged (being disconnected and with no torque transmitted), the pressure plate 31 is displaced rightward in FIG. 4 (in the direction in which the pressing portion 31B of the pressure plate 31 is displaced apart from the pressing portion 27B of the inner driver 27) by a push rod 35 discussed later. The pressing portion 31B of the pressure plate 31 is spaced apart from the friction disc 25 positioned rightmost in FIG. 4 (positioned adjacent to the pressing portion 31B of the pressure plate 31).
When the friction clutch 1 is being engaged, the pressure plate 31 is displaced and urged toward the flange 27A of the inner driver 27 by the compression springs 33. The friction discs 25 and the clutch plates 29 are interposed and pressed between the pressing portion 27B of the inner plate 27 and the pressing portion 31B of the pressure plate 31 to generate frictional force between each friction disc 25 and clutch plate 29. This allows torque to be transmitted from the outer driver 23 to the inner driver 27.
Next will be described the conventional clutch engagement control system 200.
The conventional clutch engagement control system 200 comprises the actuator 3. The actuator 3 and the compression springs 33 displace the pressure plate 31 in the rotational axis direction of the mission shaft 7. Based on the displacement, the friction clutch 1 is engaged (with torque transmitted) or disengaged (with no torque transmitted).
The pressure plate 31 has a center portion engaging with one end of the push rod 35 via a deep groove ball bearing 37, for example, and also can rotate around the push rod 35. The other end of the push rod 35 engages with one end of the cylindrical mission shaft 7 positioned inside thereof.
When force larger than the urging force produced by the compression springs 33 displaces the push rod 35 rightward in FIG. 4 (in the rotational axis direction of the mission shaft 7 in which the pressing portion 31B of the pressure plate 31 is spaced apart from the pressing portion 27B of the inner driver 27), the push rod 35 pushes and displaces the pressure plate 31 in the same manner accordingly.
On the other hand, when the push rod 35 is displaced leftward in FIG. 4, the pressure plate 31 pushes the push rod 35 by urging force produced by the compression springs 33 and is also displaced in the same manner.
Inside the cylindrical mission shaft 7, a ball 39 is disposed adjacent to the other end of the push rod 35 and a push rod 41 is disposed adjacent to the ball 39.
The push rod 41 has one end 41A protruding from the other end (the end opposite to the one provided with the inner driver 27) of the cylindrical mission shaft 7.
The protruding end 41A of the push rod 41 is integrally provided with a piston 43 which is included in the actuator 3. The piston 43 is guided by a cylinder body 45 and is slidable in the rotational axis direction of the mission shaft 7.
When hydraulic oil as compressed fluid is supplied to a space 47 enclosed by the piston 43 and the cylinder body 45, the piston 43 is pressed and displaced rightward in FIG. 4. Accordingly, the pressure plate 31 is pressed rightward in FIG. 4 (in the rotational axis direction of the mission shaft 7 in which the pressing portion 31B of the pressure plate 31 is spaced apart from the pressing portion 27B of the inner driver 27) via the push rod 41, the ball 39, the push rod 35 and the deep groove ball bearing 37.
As described above, when the pressure plate 31 is pressed rightward in FIG. 4 and the pressing portion 31B of the pressure plate 31 is spaced apart from the friction discs 25, the friction clutch 1 is disengaged.
When the hydraulic oil supplied is gradually drained out of the enclosed space 47 with the friction clutch 1 being disengaged, the piston 43 is gradually displaced leftward in FIG. 4 (in the direction in which the volume of the space 47 decreases).
The reason for this displacement is because the pressure plate 31 is normally urged by the compression springs 33 so as to be displaced leftward in FIG. 4 (in the rotational axis direction of the mission shaft 7 in which the pressing portion 31B of the pressure plate 31 approaches the pressing portion 27B of the inner driver 27). This urging force also allows the piston 43 to normally be urged leftward as viewed in FIG. 4, via the deep groove ball bearing 37, the push rod 35, the ball 39 and the push rod 41.
When the piston 43 is gradually displaced leftward in FIG. 4 as described above, the pressure plate 31 is also gradually displaced leftward in FIG. 4. The pressing portion 31B of the pressure plate 31 then touches the nearest friction disc 25 of the friction discs, allowing the friction clutch 1 to start being engaged. Thus, the friction clutch 1 starts transmitting power.
When the piston 43 is further displaced leftward in FIG. 4, the pressure force of the pressure plate 31 toward the friction discs 25 increases. In other words, this allows the pressing portion 27B of the inner driver 27 and the pressing portion 31B of the pressure plate 31 to clamp the friction discs 25 and the clutch plates 29 with increased force. Subsequently sliding between the friction discs 25 and the clutch plates 29 stops, and at that time, the friction clutch 1 is fully engaged.
Decreasing the pressure of the hydraulic oil in the space 47 enclosed by the piston 43 and the cylinder body 45 with the friction clutch 1 fully engaged allows the piston 43 and the push rod 41 to be further displaced leftward in FIG. 4. The push rod 41 and the ball 39 may then be spaced apart from each other. Even in such case, the position of the pressure plate 31 relative to the inner driver 27 stays nearly the same as in the case that the friction clutch 1 is fully engaged, or almost remains unchanged.
Supply or drainage of hydraulic oil to or from the space 47 enclosed by the piston 43 and the cylinder body 45 is performed through a master cylinder 53 comprising a reserve tank 51 and connected to the space 47 via a hydraulic oil passage 49 made up of pipes.
The master cylinder 53 comprises a master cylinder body 57 and a piston 55 engaging and sliding with the master cylinder body 57. The piston 55 has one end protruding outward of the master cylinder body 57. The piston 55 also has an end face of the end touching one end face of an output shaft 61 of a small actuator 59.
The small actuator 59 including a small hydraulic cylinder and a small control motor operates under the control of a control device (not shown) comprising, for example, a ROM and a CPU for controlling the operations of the small actuator 59 based on the control patterns preset therein.
When the friction clutch 1 is disengaged, the output shaft 61 of the small actuator 59 is displaced leftward in FIG. 4 (in the direction in which the output shaft 61 protrudes). The displacement of the output shaft 61 allows the piston 55 to be pressed leftward in FIG. 4. Therefore, the volume in a space 63 enclosed by the master cylinder body 57 and the piston 55 decreases. This decrease in volume allows the hydraulic oil staying in the space 63 to run through the hydraulic oil passage 49 and to be supplied to the space 47 enclosed by the cylinder body 45 and the piston 43. The piston 43 is then displaced rightward in FIG. 4.
The rightward displacement of the piston 43 allows the pressure plate 31 to be pressed rightward in FIG. 4 via the push rod 41, the ball 39, the push rod 35, and the deep groove ball bearing 37. This pressed force is larger than force produced by the compression springs 33 to urge the pressure plate 31 leftward in FIG. 4, which results in rightward displacement of the pressure plate 31 in FIG. 4. The pressing portion 31B of the pressure plate 31 is spaced apart from the friction discs 25, and the friction clutch 1 is then disengaged.
Next, description will be made of the example in which the friction clutch 1 is reengaged.
When the friction clutch 1 is being disengaged, the piston 43 of the actuator 3 presses the pressure plate 31 rightward in FIG. 4 via the push rod 41, the ball 39, the push rod 35 and the deep groove ball bearing 37. The pressing portion 31B of the pressure plate 31 remains apart from the friction discs 25. Even under this condition, the pressure plate 31 is urged leftward in FIG. 4 by the compression springs 33 so that the piston 43 is urged leftward in FIG. 4 via the deep groove ball bearing 37, the push rod 35, the ball 39 and the push rod 41.
The urged piston 43 further allows the piston 55 of the master cylinder 53 to be urged rightward in FIG. 4 (in the direction in which the piston 55 presses the output shaft 61 of the small actuator 59) via the hydraulic oil running from the hydraulic passage 49.
When the output shaft 61 of the small actuator 59 is gradually displaced rightward in FIG. 4 (in the direction in which the output shaft 61 retracts into a small actuator body 65) with the friction clutch 1 being disengaged, the piston 55 pressed by the output shaft 61 of the small actuator 59 is accordingly displaced rightward in FIG. 4. The displacement of the piston 55 results in a flow of hydraulic oil from the space 47 enclosed by the cylinder body 45 and the piston 43 to the space 63 enclosed by the master cylinder body 57 and the piston 55 through the hydraulic oil passage 49.
The displacement of hydraulic oil allows the piston 43 urged by the pressure plate 31 and the compression springs 33 to be gradually displaced leftward in FIG. 4. Accordingly, the pressure plate 31 is also gradually displaced leftward in FIG. 4 and shortly starts engaging the friction clutch 1 (start transmitting power). When the pressure plate 31 is further displaced leftward in FIG. 4, the urging force produced by the compression springs 33 results in increased frictional force generated between the friction discs 25 and the clutch plates 29. Slipping between the friction discs 25 and the clutch plates 29 further reduces, and then the friction clutch I is fully engaged.
The cylinder body 45 of the actuator 3, the master cylinder body 57 of the master cylinder 53, and the small actuator body 65 of the small actuator 59 are fixed integrally, for example, to the engine gear case CS1 respectively.
The displacement of hydraulic oil allows the piston 43 urged by the pressure plate 31 and the compression springs 33 to be gradually displaced leftward in FIG. 4. Accordingly, the pressure plate 31 is also gradually displaced leftward in FIG. 4 and shortly starts engaging the friction clutch 1 (starts transmitting power). When the pressure plate 31 is further displaced leftward in FIG. 4, the urging force produced by the compression springs 33 results in increased frictional force generated between the friction discs 25 and the clutch plates 29. Slipping between the friction discs 25 and the clutch plates 29 further reduces, and then the friction clutch 1 is fully engaged.
Next will be described the engagement velocity at which the conventional clutch engagement control system 200 reengages the friction clutch 1.
FIG. 5 illustrates an example of engagement velocity at which the conventional clutch engagement control system 200 reengages the friction clutch 1.
The horizontal axis and the vertical axis of FIG. 5 represent elapsed time and displacement of the output shaft 61 of the small actuator 59, respectively. The upward (positive) direction in the vertical axis of FIG. 5 corresponds to the rightward displacement of the output shaft 61 in FIG. 4 (in the direction in which the output shaft 61 retracts into the small actuator body 65).
For example, when the friction clutch I is reengaged to start the motorcycle moving, the output shaft 61 starts to be displaced rightward in FIG. 4 at time t11 and continues to be displaced at relatively high velocity, V11, until time t12. Until the motorcycle starts moving, the gear 21, the outer driver 23 and the friction discs 25 shown in FIG. 4 are rotating according to the engine rotation while the clutch plates 29, the inner driver 27 and the pressure plate 31 are not rotating.
When the friction clutch 1 is being disengaged, normally there is a gap of approximately 2 mm between the pressing portion 31B of the pressure plate 31 shown in FIG. 4 and the friction disc 25 positioned rightmost in FIG. 4. The reason for the displacement at high velocity, V11, is to reduce the time required for engaging the friction clutch 1, which is achieved by displacing the pressing portion 31B by the major portion of the distance in the gap at as high a velocity as possible.
For example, when the friction clutch 1 is reengaged to start the motorcycle moving, the output shaft 61 starts to be displaced rightward in FIG. 4 at the time til and continues to be displaced at relatively high velocity, Vii, until time t12. Until the motorcycle starts moving, the gear 21, the outer driver 23 and the friction discs 25 shown in FIG. 4 are rotating according to the engine rotation while the clutch plates 29, the inner driver 27, and the pressure plate 31 are not rotating.
The rightward displacement of the output shaft 61 in FIG. 4 continues at velocity V12. This allows the pressure plate 31 to be displaced in the direction (leftward in FIG. 4) so as to approach the pressing portion 27B of the inner driver 27 at velocity corresponding to the velocity V12 (or at velocity corresponding to the ratio between pressed areas of the piston 57 of the master cylinder 53 and of the piston 43 of the actuator 3). Then, the point to start engaging the clutch, P11, is reached at t13.
At the point to start engaging the clutch, P11, the pressing portion 31B of the pressure plate 31 touches the friction disc 25 (positioned adjacent to the pressing portion 31B) and torque starts to be transmitted between the friction discs 25 and the pressure plates 29.
Then, the rightward displacement of the output shaft 61 in FIG. 4 further continues at velocity V12, which results in a moderate enhancement of power transmissibility between the friction discs 25 and the pressure plates 29. The point at which the clutch is fully almost engaged with almost no slipping therebetween, P12, is reached at time t14. Following that, the displacement velocity of the output shaft 61 is increased to velocity V13 after a predetermined time period, that is, at time t15.
The point to start engaging the clutch, P11, varies depending on temperature as well as on how much the friction discs 25 and the clutch plates 29 wear out by engaging and disengaging the friction clutch 1.
If the point to start engaging the clutch varies from P11 at time t13 to P21 at t21, the point at which the clutch is fully engaged, P22, is also reached earlier, at time t22 before the point P12, due to the earlier start of clutch engagement. Thus, the displacement velocity of the output shaft 61 may be increased at time t23 to velocity V13 as shown by dashed lines in FIG. 5.
However, the point to start engaging the clutch varies depending on temperature as described above, there may be a case where the point to start engaging the clutch is delayed to P31 at time t31. In this case, if the output shaft 61 of the small actuator 59 is still displaced at high velocity, V13, at time t23 as shown by dashed lines in FIG. 5, the pressing portion 31B of the pressure plate 31 suddenly presses the friction discs 25 before the friction clutch 1 is fully connected, that is, before the friction clutch 1 is fully engaged. Then, the friction clutch 1 is suddenly connected, in other words, the friction clutch 1 is suddenly and fully engaged. This sharply increases the rotational speed of the rear wheel 13 connected to the engine (not shown) via the mission shaft 7 and the countershaft 9 and causes shock when the motorcycle starts.
In other situations, the engine can be stopped due to a sharp increase in load applied to the engine.
Therefore, the conventional clutch engagement control system 200 allows sufficient time between times t12 and t15, by using a long preset time period between times t12 and t15.
The above description of FIG. 5 indicates that the engagement velocity of the friction clutch 1 is represented on the vertical axis so as to designate the displacement of the output shaft 61 of the small actuator 59. But it is not limited to that.
For example, the graph of FIG. 5 can also be used to represent the engagement velocity of other components For example, FIG. 5 can be used to represent the displacements of the pressure plate 31, the push rod 35 and the push rod 41 in the rotational axis direction of the mission shaft 7, and the displacements of the piston 43 of the actuator 3 and that of the piston 57 of the master cylinder 53.
However, using parameters other than the displacement of the output shaft 61 of the small actuator 59 to indicate the engagement velocity of the friction clutch 1 results in almost no positive value of the velocity V13 in FIG. 5 (the portion showing the velocity of the output shaft 61 after the friction clutch 1 was fully engaged).
The reason for an almost zero value is because the pressure plate 31 is no longer displaced after the friction clutch 1 is fully engaged. Accordingly, the push rod 35 is no longer pressed and displaced by the pressure plate 31.
In order to allow the conventional clutch engagement control system 200 to perform engagement control of the friction clutch 1 without shock for engaging the clutch, even if the point to start engaging the friction clutch varies depending on temperature, a relatively long time is required to slowly displace the pressure plate 31 at around the point to start engaging the clutch.
In the example of the conventional system, the description is made of the problems when the motorcycle starts, however, using the multistage transmission 5 for shifting gears also causes the same problems.